Your stand is absolutely gorgeous. But one thing would make me worry, the whole weight of the tank is supported mainly be the 4 legs. The 2x4' between the legs are only held up with the screws, therefore putting alot of pressure on these screws.
This might be OK in your case since you have a terrarium, therefore not as heavy as a fully filled aquarium. But this design would worry me on a stand that should carry a filled tank.